Project description:Somatic stem cells mediate tissue maintenance for the lifetime of an organism. Despite the well-established longevity that is a prerequisite for such function, accumulating data argue for compromised stem cell function with age. Identifying the mechanisms underlying age-dependent stem cell dysfunction is therefore key to understand the aging process. Using a model that carries a proofreading defective mitochondrial DNA polymerase, we demonstrate hematopoietic defects reminiscent of premature HSC aging including anemia, lymphopenia and myeloid lineage skewing. However, in contrast to physiologic stem cell aging, rapidly accumulating mitochondrial DNA mutations displayed little involvement of the hematopoietic stem cell pool but rather with distinct differentiation blocks and/or disappearance of downstream progenitors. Hematopoietic stem cells (HSC) has been sorted out from midaged wildtype and mutator mice and compared with stem cells sorted from young and and old wt mice
Project description:Somatic stem cells mediate tissue maintenance for the lifetime of an organism. Despite the well-established longevity that is a prerequisite for such function, accumulating data argue for compromised stem cell function with age. Identifying the mechanisms underlying age-dependent stem cell dysfunction is therefore key to understand the aging process. Using a model that carries a proofreading defective mitochondrial DNA polymerase, we demonstrate hematopoietic defects reminiscent of premature HSC aging including anemia, lymphopenia and myeloid lineage skewing. However, in contrast to physiologic stem cell aging, rapidly accumulating mitochondrial DNA mutations displayed little involvement of the hematopoietic stem cell pool but rather with distinct differentiation blocks and/or disappearance of downstream progenitors.
Project description:The premature aging disorder Werner Syndrome (WS) is characterized by early onset of aging phenotypes resembling natural aging. In most WS patients there are mutations in the DNA helicase WRN, an enzyme important in maintaining genome stability and telomere replication. Interestingly, its clinical manifestations reflect a severe degree of deterioration for connective tissue, whereas the central nervous system is less affected. We suggest that the varied vulnerability to aging is regulated by an unknown mechanism that protects specific lineages of stem cells from premature senescence. To address this problem, we reprogrammed patient skin fibroblasts to induced pluripotent stem cells (iPSC). The expression profile for the differentiated normal and WS fibroblasts and undifferentiated iPSC were compared. A distinct expression profile was found between normal and WS fibroblasts, however, few changes of gene expression were found in iPSC. Our findings suggest an erasure of aging phenotype associated with WS in reprogrammed iPSC. Human normal and WS skin fibroblasts were reprogrammed to induced pluripotent stem cells (iPSC). These samples, before and after reprogramming, were analyzed for the change of gene expression profile.
Project description:The premature aging disorder Werner Syndrome (WS) is characterized by early onset of aging phenotypes resembling natural aging. In most WS patients there are mutations in the DNA helicase WRN, an enzyme important in maintaining genome stability and telomere replication. Interestingly, its clinical manifestations reflect a severe degree of deterioration for connective tissue, whereas the central nervous system is less affected. We suggest that the varied vulnerability to aging is regulated by an unknown mechanism that protects specific lineages of stem cells from premature senescence. To address this problem, we reprogrammed patient skin fibroblasts to induced pluripotent stem cells (iPSC). The expression profile for the differentiated normal and WS fibroblasts and undifferentiated iPSC were compared. A distinct expression profile was found between normal and WS fibroblasts, however, few changes of gene expression were found in iPSC. Our findings suggest an erasure of aging phenotype associated with WS in reprogrammed iPSC.
Project description:Dyskeratosis congenita (DKC) and idiopathic aplastic anemia (AA) are bone marrow failure syndromes that share characteristics of premature aging with severe telomere attrition. In this study, we analyzed blood samples of 62 AA and 13 DKC patients to demonstrate that their epigenetic age predictions are overall increased, albeit not directly correlated with telomere length. Aberrant DNA methylation was observed in the gene PRDM8 in DKC and AA as well as in other diseases with premature aging phenotype, such as Down syndrome, Werner syndrome and Hutchinson-Gilford-Progeria syndrome. To gain further insight into the functional relevance of PRDM8 we generated induced pluripotent stem cells (iPSCs) with heterozygous and homozygous knockout. Loss of PRDM8 impaired hematopoietic and neuronal differentiation of iPSCs, but it did not impact on epigenetic age. Taken together, aberrant DNA methylation in PRDM8 provides a biomarker for bone marrow failure syndromes, which may contribute to the hematopoietic and neuronal phenotypes of premature aging syndromes.
Project description:Dyskeratosis congenita (DKC) and idiopathic aplastic anemia (AA) are bone marrow failure syndromes that share characteristics of premature aging with severe telomere attrition. In this study, we analyzed blood samples of 62 AA and 13 DKC patients to demonstrate that their epigenetic age predictions are overall increased, albeit not directly correlated with telomere length. Aberrant DNA methylation was observed in the gene PRDM8 in DKC and AA as well as in other diseases with premature aging phenotype, such as Down syndrome, Werner syndrome and Hutchinson-Gilford-Progeria syndrome. To gain further insight into the functional relevance of PRDM8 we generated induced pluripotent stem cells (iPSCs) with heterozygous and homozygous knockout. Loss of PRDM8 impaired hematopoietic and neuronal differentiation of iPSCs, but it did not impact on epigenetic age. Taken together, aberrant DNA methylation in PRDM8 provides a biomarker for bone marrow failure syndromes, which may contribute to the hematopoietic and neuronal phenotypes of premature aging syndromes.
Project description:Recurrent somatic mutations in a subset of spliceosome genes (SF3B1, SRSF2, and U2AF1) are frequently identified in patients with myeloid malignancies such as myelodysplastic syndromes (MDS). These heterozygous and mutually exclusive mutations are enriched in hotspot codons in these 3’ splicing factor proteins resulting in aberrant alternative mRNA splicing in hematopoietic cells. However, each mutant protein predominantly affects a distinct set of alternatively spliced downstream target genes suggesting that global mRNA splicing alterations, rather than specific splicing targets, may be responsible for MDS phenotypes, including dysplasia, ineffective hematopoiesis, and cytopenias. U2AF1 provides a unique opportunity to address this question because it has two hotspot positions (serine 34 [S34] and glutamine 157 [Q157]) that are each commonly mutated in MDS and are associated with unique mRNA splicing consequences. In addition, U2AF1 S34 and Q157 codon mutations co-occur with mutations in different genes (e.g., BCOR and ASXL1, respectively) and patients with these mutations may have different hematopoietic phenotypes—highlighting that these mutations may induce distinct phenotypes. We asked if the splicing differences resulting from S34F and Q157R mutations were thus associated with different or similar effects on hematopoiesis. To do so, we engineered a new Cre/lox conditional mouse model with the Q157R mutation knocked-in to the endogenous U2af1 locus based on our established conditional S34F knock-in mouse model and utilized both models to directly study the hematopoietic phenotype, transcriptional, and mRNA splicing consequences of individual U2AF1 gene mutations in vivo. Our results indicate that the two mutations induce distinct hematopoietic phenotypes in mice, suggesting that the U2af1S34F and U2af1Q157R mutations should not be conflated as they may impact disease pathogenesis differently in patients. Mice expressing U2af1S34F have a more severe reduction in their PB and BM cell counts, and reduced HSPCs repopulating ability, compared to mice expressing U2af1Q157R. The expression and splicing of the majority of target genes are unique between the mutations, in both mouse and human samples, potentially driving the phenotypic differences induced by the two mutations. The two mutations co-occur with different gene mutations and are not equally represented in various myeloid neoplasms, suggesting that multiple mechanisms are likely to drive the pathogenesis of U2AF1 mutant myeloid diseases. Collectively, our results support that U2AF1S34F and U2AF1Q157R mutations induce distinct hematopoietic, gene expression, and RNA splicing phenotypes in vivo, suggesting that larger prospective studies are needed to understand if patients with these mutations should be classified differently.
Project description:Zmpste24 is a metalloproteinase processing prelamin A into mature lamin A, a nuclear structure protein. Zmpste24-/- mice which accumulate prelamin A in cells recapitulate accelerated aging phenotypes observed in human premature aging disorder, Hutchinson Gilford progeria sydrome (HGPS). Zmpste24-/- mouse embryonic fibroblasts (MEFs) exhibited genomic instabiliy and accelerated aging at cellular level, which is premature senescence. We performed microarray analysis on Zmpste24-/- MEFs, compared to wild-type littermates' MEFs, at an early passage (P3), which is a pre-symptom stage before cellular senescence occurs in the mutant MEFs, in order to examine gene expression profile and figure out the underneath mechanism triggering the premature aging process. Early passage wild-type and Zmpste24-/- MEFs were collected for RNA extraction, the quality of RNAs were determinded by Electrophoresis Assay (2100 Bioanalyzer, Agilent) and RNA extractions were used for hybridization on Affymetrix microarrays.
Project description:Aging is a consequence of complex molecular changes, but the roles for individual microRNAs (miRNAs) in aging remain unclear. One of the few miRNAs that is upregulated during both normal and premature aging is miR-29. We confirmed this finding in our study in both mouse and monkey models. Follow-up analysis of the transcriptomic changes during normal aging revealed that miR-29 is among the top miRNAs predicted to drive the aging-related gene expression changes. We also showed that partial loss of miR-29 extends the lifespan of Zmpste-/- mice, an established model of progeria, which indicates that miR-29 is functionally important in this accelerated aging model. To examine whether miR-29 upregulation alone is sufficient to promote aging-related phenotypes in vivo, we generated mice in which miR-29 can be conditionally overexpressed (miR-29TG). We found that miR-29 overexpression in mice is sufficient to drive aging-related phenotypes including alopecia, kyphosis, osteoporosis and senescence, and leads to early lethality. Transcriptomic analysis of both young miR-29TG and old WT mice revealed shared downregulation of genes enriched in extracellular matrix and fatty acid metabolism, and shared upregulation of genes in pathways linked to inflammation. Together, these results highlight the functional importance of miR-29 in controlling a gene expression program that drives aging-related phenotypes.
Project description:Hutchinson-Gilford progeria syndrome (HGPS) is a rare and fatal human premature aging disease1-5, characterized by premature atherosclerosis and degeneration of vascular smooth muscle cells (SMCs)6-8. HGPS is caused by a single-point mutation in the LMNA gene, resulting in the generation of progerin, a truncated mutant of lamin A. Accumulation of progerin leads to various aging-associated nuclear defects including disorganization of nuclear lamina and loss of heterochromatin9-12. Here, we report the generation of induced pluripotent stem cells (iPSCs) from fibroblasts obtained from patients with HGPS. HGPS-iPSCs show absence of progerin, and more importantly, lack the nuclear envelope and epigenetic alterations normally associated with premature aging. Upon differentiation of HGPS-iPSCs, progerin and its associated aging consequences are restored. In particular, directed differentiation of HGPS-iPSCs to SMCs leads to the appearance of premature senescent SMC phenotypes associated with vascular aging. Additionally, our studies identify DNA-dependent protein kinase catalytic subunit (DNAPKcs) as a component of the progerin-containing protein complex. The absence of nuclear DNAPKcs correlates with premature as well as physiological aging. Since progerin also accumulates during physiological aging6,12,13, our results provide an in vitro iPSC-based model with an acceleration progerin accumulation to study the pathogenesis of human premature and physiological vascular aging. Microarray gene expression profiling was done to: (1) Compare differences between WT fibroblasts and fibroblasts from patients suffering of the Hutchinson-Gilford progeria syndrome (2) Check that iPSC originating from WT and patients are in fact similar to ESC